As shown in FIG. 1, a capacitive touch panel 10 has a plurality of traces 14, 16, 18, 20 and 22 in X-direction, which are assigned with the coordinates X1, X2, X3, X4 and X5 respectively, from the boundary 12 to the right. Each coordinate Xm represents where the center of the corresponding trace is in the X-direction, and the coordinate Xm may be a relative coordinate or an absolute coordinate in the X-direction. When the capacitive touch panel 10 is touched, the capacitances of the touched traces are changed. By sensing the traces 14, 16, 18, 20 and 22 for the capacitances thereon, the measured capacitances Cm, typically converted by an analog-to-digital converter (not shown in FIG. 1) into digital values, are used together with the coordinate Xm for interpolation to position the touch point at the coordinate
                              X          =                                    ∑                              m                =                1                            n                        ⁢                                          (                                                      X                    m                                    ×                                      C                    m                                                  )                            /                                                ∑                                      m                    =                    1                                    n                                ⁢                                  C                  m                                                                    ,                            [                  Eq          ⁢                      -                    ⁢          1                ]            where n is the number of the traces. However, this method is good only for positioning the touch points within the range 24. If the usable area of the capacitive touch panel 10 is extended to the boundary 12 for hardware-related reasons, due to the coordinates Xm of the traces 14, 16, 18, 20 and 22 all defined in correspondence to their respective centers, any touch points around the boundary 12 and beyond (i.e., to the left of) the center X1 of the boundary trace 14 cannot be positioned precisely by the above interpolation algorithm and thus a non-addressable region 26 is present. All capacitive touch panels have such non-addressable regions at their boundaries that are useless for user's touch operation.